1. Field of the Invention
The present invention relates to a component in a processing chamber of a substrate processing apparatus, and a method of measuring a temperature of the component.
2. Description of the Related Art
In a substrate processing apparatus for performing a predetermined plasma process on a wafer constituting a substrate by using plasma generated in a processing chamber, members disposed in the processing chamber are worn away by the plasma. Specifically, an abrasion loss of a focus ring disposed to surround the wafer and formed of the same material as the wafer is high as the focus ring is exposed to plasma having relatively high density. Since a distribution of plasma on the wafer changes when the focus ring is worn away, the focus ring needs to be replaced when the abrasion loss of the focus ring exceeds a predetermined amount while monitoring the abrasion loss.
Also, conventionally, when various processes, such as a plasma process, are performed on the wafer, temperatures of the wafer and each component in the processing chamber are measured and controlled so as to promote certainty of a process. In addition, recently, technologies about a temperature measuring method that measures a temperature of a focus ring by using a low-coherence light interference thermometer have been suggested (for example, refer to Patent References 1 and 2). The low-coherence light interference thermometer measures a temperature of a target by irradiating a low-coherence light toward a rear surface of the temperature measured target, for example, a focus ring, and measuring interference between a reference light and reflection lights from a front surface and the rear surface.
However, in a temperature measuring technology using a low-coherence light interference thermometer, a measured target should satisfy requirements, such as allowing a part of a measurement light to penetrate therethrough, having a high degree of parallelization of a front surface and a rear surface at a measurement portion, and having a mirror-like finished front surface and rear surface. Accordingly, when the measured target is worn away by plasma and the degree of parallelization of the surface and rear surface is no longer maintained, requirements of the measured target are not satisfied, and thus a temperature cannot be accurately measured.
Also, conventional suggestions about a temperature measuring technology using a low-coherence light interference thermometer are mainly about improving a low-coherence light interference thermometer, and studies about making a measured target suitable for temperature measurement using a low-coherence light interference thermometer have not been performed.    (Patent Document 1) Japanese Laid-Open Patent Publication No. 2008-227063    (Patent Document 2) Japanese Laid-Open Patent Publication No. 2003-307458